Supplemental device for attachment to an injection device

ABSTRACT

A supplemental device for attachment to an injection device including a dosage window covering a sleeve on which dose values are marked is provided. The supplemental device comprises: a main body; an arrangement for supporting the main body of the supplemental device in a predetermined positional relationship with the injection device; a transparent protection window located at a surface of the main body that is aligned with the dosage window of the injection pen when in use; and a sensor arrangement supported in the main body and having a sensor directed at the protection window. The protection window has an optical power. The protection window may be a cylindrical lens or a toric lens.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of and claims the benefit ofpriority under 35 U.S.C. § 120 to U.S. application Ser. No. 14/779,547,filed Sep. 23, 2015, which is a U.S. National Phase Application pursuantto 35 U.S.C. § 371 of International Application No. PCT/EP2013/058322filed Apr. 22, 2013. The entire disclosure contents of each of theseapplications are herewith incorporated by reference into the presentapplication.

FIELD OF INVENTION

The present invention relates to a supplemental device for attachment toan injection device.

BACKGROUND

A variety of diseases exists that require regular treatment by injectionof a medicament. Such injection can be performed by using injectiondevices, which are applied either by medical personnel or by patientsthemselves. As an example, type-1 and type-2 diabetes can be treated bypatients themselves by injection of insulin doses, for example once orseveral times per day. For instance, a pre-filled disposable insulin pencan be used as an injection device. Alternatively, a re-usable pen maybe used. A re-usable pen allows replacement of an empty medicamentcartridge by a new one. Either pen may come with a set of one-wayneedles that are replaced before each use. The insulin dose to beinjected can then for instance be manually selected at the insulin penby turning a dosage knob and observing the actual dose from a dosewindow or display of the insulin pen. The dose is then injected byinserting the needle into a suited skin portion and pressing aninjection button of the insulin pen. To be able to monitor insulininjection, for instance to prevent false handling of the insulin pen orto keep track of the doses already applied, it is desirable to measureinformation related to a condition and/or use of the injection device,such as for instance information on the injected insulin type and dose.

It has been described, for instance in WO 2011/117212 to provide asupplementary device comprising a mating unit for releasably attachingthe device to an injection device. The device includes a camera and isconfigured to perform optical character recognition (OCR) on capturedimages visible through a dosage window of the injection pen, thereby todetermine a dose of medicament that has been dialed into the injectiondevice.

SUMMARY

A first aspect of the invention provides a supplemental deviceconfigured for attachment to an injection the supplemental devicecomprising:

a main body;

an arrangement for supporting the main body of the supplemental devicein a predetermined positional relationship with the injection device;

a transparent protection window located at a surface of the main body;and

a sensor arrangement supported in the main body and having a sensordirected at the protection window,

wherein the protection window is configured as a cylindrical lens or atoric lens with an optical power.

This arrangement can correct for pin cushion distortion provided by thesensor arrangement, the distance between the sensor arrangement and thedosage window and/or the curved shape of a sleeve that is viewablethrough the protection window. Moreover, this can be achieved through asimple and inexpensive arrangement.

The protection window may be configured as a toric lens, or it may beconfigured as a cylindrical lens. A cylindrical lens may be easier toproduce. Both may have similar ability to correct pin cushiondistortion.

A first portion of the protection window may be configured as acylindrical or toric lens and wherein a second portion of the protectionwindow has a different optical power to the first portion. This canallow part of the protection window that is used in the optical imagingsystem to have the optical power needed to reduce pin cushion distortionwhilst allowing the second portion not to be required to have theoptical power. The second portion may be used for illuminating thesleeve visible through the dosage window and/or for mechanical supportfor the first portion.

The supplemental device may comprise an illumination arrangementcomprising one or more sources of light, each of the one or more sourcesof light being directed at the protection window. This can improveoperation of the sensor arrangement. The protection window can assist inilluminating the sleeve visible through the dosage window.

The supplemental device may comprise an illumination arrangementcomprising one or more sources of light, each of the one or more sourcesof light being directed at the protection window, wherein a firstportion of the protection window may be configured as a cylindrical ortoric lens, wherein a second portion of the protection window has adifferent optical power to the first portion. The first portion of theprotection window may be in the optical path between the sensorarrangement and the dosage window of the injection pen when the deviceis in use. The second portion of the protection window may be not in theoptical path between the sensor arrangement and the dosage window of theinjection pen when the device is in use. The second portion of theprotection window may be in the optical path between the illuminationarrangement and the dosage window of the injection pen when the deviceis in use.

The supplemental device may comprise an illumination arrangementcomprising two or more sources of light, each of the two or more sourcesof light being directed at the protection window, wherein the two ormore sources of light are located on opposite sides of the sensorarrangement, wherein a central portion of the protection window may beconfigured as a cylindrical or toric lens, wherein a periphery portionof the protection window has a different optical power to the centralportion, wherein the central portion of the protection window may be inthe optical path between the sensor arrangement and the dosage window ofthe injection pen when the device is in use, and wherein the peripheryportion of the protection window may be not in the optical path betweenthe sensor arrangement and the dosage window of the injection pen whenthe device is in use but may be in the optical path between theillumination arrangement and the dosage window of the injection pen whenthe device is in use.

The transparent protection window may be formed of optical plastic. Thiscan allow the transparent protection window to be providedinexpensively.

The transparent protection window may be provided with ananti-reflective coating on at least one surface thereof. This canimprove the optical imaging arrangement and provide more reliablereading of a sleeve visible through the dosage window. Theanti-reflective coating may comprise plural dielectric layers. This canremove reflexes effectively in a stable arrangement. The anti-reflectivecoating may comprise between three and five dielectric layers.

The protection window may be sealed to the main body so as to preventthe ingress of material into the supplemental device around theprotection window. This can avoid the need for a separate sealingarrangement.

Another aspect of the invention provides a system comprising asupplemental device as above and an injection device. Here, a surface ofthe protection window that is furthest from the sensor arrangement maylie on a curved surface of an imaginary cylinder having an axiscoincident with a longitudinal axis of the injection device and thesurface of the protection window that is furthest from the sensorarrangement may lie in close proximity with a dosage window of theinjection device when the supplemental device is installed on theinjection device. This can contribute to a compact arrangement for thesupplemental device.

A second aspect of the invention provides a supplemental device forattachment to an injection device including a dosage window covering asleeve on which dose values are marked, the supplemental devicecomprising:

a main body;

an arrangement for supporting the main body of the supplemental devicein a predetermined positional relationship with the injection device;

a transparent protection window located at a surface of the main bodythat is aligned with the dosage window of the injection pen when in use;and

a sensor arrangement supported in the main body and having a sensordirected at the protection window,

wherein the protection window has an optical power.

This arrangement can correct for pin cushion distortion provided by thesensor arrangement, the distance between the sensor arrangement and thedosage window and/or the curved shape of a sleeve that is viewablethrough the protection window. Moreover, this can be achieved through asimple and inexpensive arrangement.

The protection window may be configured as a toric lens, or it may beconfigured as a cylindrical lens. A cylindrical lens may be easier toproduce. Both may have similar ability to correct pin cushiondistortion.

A first portion of the protection window may have the optical power anda second portion of the protection window may have a different opticalpower to the first portion. This can allow part of the protection windowthat is used in the optical imaging system to have the optical powerneeded to reduce pin cushion distortion whilst allowing the secondportion not to be required to have the optical power. The second portionmay be used for illuminating the sleeve visible through the dosagewindow and/or for mechanical support for the first portion.

The supplemental device may comprise an illumination arrangementcomprising one or more sources of light, each of the one or more sourcesof light being directed at the protection window. This can improveoperation of the sensor arrangement. The protection window can assist inilluminating the sleeve visible through the dosage window.

The supplemental device may comprise an illumination arrangementcomprising one or more sources of light, each of the one or more sourcesof light being directed at the protection window, wherein a firstportion of the protection window has the optical power, wherein a secondportion of the protection window has a different optical power to thefirst portion, wherein the first portion of the protection window may bein the optical path between the sensor arrangement and the dosage windowof the injection pen when the device is in use, and wherein the secondportion of the protection window may be not in the optical path betweenthe sensor arrangement and the dosage window of the injection pen whenthe device is in use but may be in the optical path between theillumination arrangement and the dosage window of the injection pen whenthe device is in use.

The supplemental device may comprise an illumination arrangementcomprising two or more sources of light, each of the two or more sourcesof light being directed at the protection window, wherein the two ormore sources of light are located on opposite sides of the sensorarrangement, wherein a central portion of the protection window has theoptical power, wherein a periphery portion of the protection window hasa different optical power to the central portion, wherein the centralportion of the protection window may be in the optical path between thesensor arrangement and the dosage window of the injection pen when thedevice is in use, and wherein the periphery portion of the protectionwindow may be not in the optical path between the sensor arrangement andthe dosage window of the injection pen when the device is in use but maybe in the optical path between the illumination arrangement and thedosage window of the injection pen when the device is in use.

The transparent protection window may be formed of optical plastic. Thiscan allow the transparent protection window to be providedinexpensively.

The transparent protection window may be provided with ananti-reflective coating on at least one surface thereof. This canimprove the optical imaging arrangement and provide more reliablereading of a sleeve visible through the dosage window. Theanti-reflective coating may comprise plural dielectric layers. This canremove reflexes effectively in a stable arrangement. The anti-reflectivecoating may comprise between three and five dielectric layers.

The protection window may be sealed to the main body so as to preventthe ingress of material into the supplemental device around theprotection window. This can avoid the need for a separate sealingarrangement.

Another aspect of the invention provides a system comprising thesupplemental device and an injection device. Here, a surface of theprotection window that is furthest from the sensor arrangement may lieon a curved surface of an imaginary cylinder having an axis coincidentwith a longitudinal axis of the injection device and the surface of theprotection window that is furthest from the sensor arrangement may liein close proximity with a dosage window of the injection device when thesupplemental device is installed on the injection device. This cancontribute to a compact arrangement for the supplemental device.

Embodiments of the invention will now be described, by way of exampleonly, with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The figures show:

FIG. 1a is an exploded view of an injection device;

FIG. 1b shows a perspective view of some detail of the injection deviceof FIG. 1 a;

FIG. 2a : a schematic illustration of a supplementary device to bereleasably attached to the injection device of FIG. 1a according to anembodiment of the present invention;

FIG. 2b : a perspective view of a supplementary device to be releasablyattached to the injection device of FIG. 1a according to variousembodiments of the present invention;

FIG. 2c : a perspective view of a supplementary device to be releasablyattached to the injection device of FIG. 1a according to otherembodiments of the present invention;

FIGS. 3A and 3 b: possible distributions of functions among devices whenusing a supplementary device (such as the supplementary devices of FIGS.2a and 2b ) together with an injection device;

FIG. 4: a schematic view of the supplementary device of FIG. 2a in astate where it is attached to the injection device of FIG. 1 a;

FIG. 5a : a flowchart of a method used in various embodiments;

FIG. 5b : a flowchart of a further method used in various embodiments;

FIG. 5c : a flowchart of a still further method used in variousembodiments;

FIG. 6: a schematic illustration of a tangible storage medium 60according to an embodiment of the present invention; and

FIG. 7: an information sequence chart that illustrates an informationflow between various devices according to embodiments of the invention;

FIG. 8 is a side view of the supplemental device of FIG. 2b attached tothe injection pen of FIG. 1 a;

FIG. 9 is a side view of the supplemental device in the same view asFIG. 8 although with the injection pen omitted and with a closure open;

FIG. 10 is a cross-section view through the arrangement of thesupplemental device and the injection pen of FIG. 8 prior to engagementof the supplemental device on the injection device;

FIG. 11a is a partial cutaway perspective view of a detail from FIG. 10;

FIG. 11b is a partial cutaway perspective view of another detail fromFIG. 10;

FIG. 12 is a cross-sectional view which is the same as FIG. 10 althoughwith the supplemental device mated to the injection device;

FIG. 13 is a cross-sectional view through the supplemental device ofFIG. 2b at a location further along the device from the cross-sectionshown in FIG. 10; and

FIG. 14 is the same cross-section as shown in FIG. 13 although with thesupplemental device installed on an injection pen and clamped in place;

FIG. 15: a cross-sectional view through the supplemental device wheninstalled on an injection pen, the cross-section being through a cameraand optical system;

FIG. 16a : a left end view of a protective window of the optical system;

FIG. 16b : a plan view of the protective window;

FIG. 16c : a right end view of the protective window;

FIG. 16d : a section A-A of FIG. 16 b;

FIG. 16e : a side view of the protective window;

FIG. 16f : a section B-B of FIG. 16 b;

FIG. 17: a plan view indicating a location of the camera with respect tothe injection pen when the supplemental device is installed;

FIG. 18: a view similar to FIG. 16 and including the protection window;and

FIGS. 19a and 19b are drawings showing respectively distortion with andwithout the protection window in place.

DETAILED DESCRIPTION

In the following, embodiments of the present invention will be describedwith reference to an insulin injection device. The present invention ishowever not limited to such application and may equally well be deployedwith injection devices that eject other medicaments, or with other typesof medical devices.

FIG. 1a is an exploded view of an injection device 1, which may forinstance represent Sanofi's Solostar® insulin injection pen.

The injection device 1 of FIG. 1a is a pre-filled, disposable injectionpen that comprises a housing 10 and contains an insulin container 14, towhich a needle 15 can be affixed. The needle is protected by an innerneedle cap 16 and an outer needle cap 17, which in turn can be coveredby a cap 18. An insulin dose to be ejected from injection device 1 canbe selected by turning the dosage knob 12, and the selected dose is thendisplayed via dosage window 13, for instance in multiples of so-calledInternational Units (IU), wherein one IU is the biological equivalent ofabout 45.5 micrograms of pure crystalline insulin ( 1/22 mg). An exampleof a selected dose displayed in dosage window 13 may for instance be 30IUs, as shown in FIG. 1a . It should be noted that the selected dose mayequally well be displayed differently. A label (not shown) is providedon the housing 10. The label includes information about the medicamentincluded within the injection device, including information identifyingthe medicament. The information identifying the medicament may be in theform of text. The information identifying the medicament may also be inthe form of a colour. The information identifying the medicament mayalso be encoded into a barcode, QR code or the like. The informationidentifying the medicament may also be in the form of a black and whitepattern, a colour pattern or shading.

Turning the dosage knob 12 causes a mechanical click sound to provideacoustical feedback to a user. The numbers displayed in dosage window 13are printed on a sleeve that is contained in housing 10 and mechanicallyinteracts with a piston in insulin container 14. When needle 15 is stuckinto a skin portion of a patient, and then injection button 11 ispushed, the insulin dose displayed in display window 13 will be ejectedfrom injection device 1. When the needle 15 of injection device 1remains for a certain time in the skin portion after the injectionbutton 11 is pushed, a high percentage of the dose is actually injectedinto the patient's body. Ejection of the insulin dose also causes amechanical click sound, which is however different from the soundsproduced when using dosage knob 12.

Injection device 1 may be used for several injection processes untileither insulin container 14 is empty or the expiration date of injectiondevice 1 (e.g. 28 days after the first use) is reached.

Furthermore, before using injection device 1 for the first time, it maybe necessary to perform a so-called “prime shot” to remove air frominsulin container 14 and needle 15, for instance by selecting two unitsof insulin and pressing injection button 11 while holding injectiondevice 1 with the needle 15 upwards.

For simplicity of presentation, in the following, it will be exemplarilyassumed that the ejected doses substantially correspond to the injecteddoses, so that, for instance when making a proposal for a dose to beinjected next, this dose equals the dose that has to ejected by theinjection device. Nevertheless, differences (e.g. losses) between theejected doses and the injected doses may of course be taken intoaccount.

FIG. 1b is a close-up of the end of the injection device 1. This Fig.shows a locating rib 70 that is located between the viewing window 13and the dosage knob 12.

FIG. 2a is a schematic illustration of an embodiment of a supplementarydevice 2 to be releasably attached to injection device 1 of FIG. 1a .Supplementary device 2 comprises a housing 20 with a mating unitconfigured and embrace the housing 10 of injection device 1 of FIG. 1a ,so that supplementary device 2 sits tightly on housing 10 of injectiondevice 1, but is nevertheless removable from injection device 1, forinstance when injection device 1 is empty and has to be replaced. FIG.2a is highly schematic, and details of the physical arrangement aredescribed below with reference to FIG. 2 b.

Supplementary device 2 contains optical and acoustical sensors forgathering information from injection device 1. At least a part of thisinformation, for instance a selected dose (and optionally a unit of thisdose), is displayed via display unit 21 of supplementary device 2. Thedosage window 13 of injection device 1 is obstructed by supplementarydevice 2 when attached to injection device 1.

Supplementary device 2 further comprises three user input transducers,illustrated schematically as a button 22. These input transducers 22allow a user to turn on/off supplementary device 2, to trigger actions(for instance to cause establishment of a connection to or a pairingwith another device, and/or to trigger transmission of information fromsupplementary device 2 to another device), or to confirm something.

FIG. 2b is a schematic illustration of a second embodiment of asupplementary device 2 to be releasably attached to injection device 1of FIG. 1a . Supplementary device 2 comprises a housing 20 with a matingunit configured and embrace the housing 10 of injection device 1 of FIG.1a , so that supplementary device 2 sits tightly on housing 10 ofinjection device 1, but is nevertheless removable from injection device1.

Information is displayed via display unit 21 of supplementary device 2.The dosage window 13 of injection device 1 is obstructed bysupplementary device 2 when attached to injection device 1.

Supplementary device 2 further comprises three user input buttons orswitches. A first button 22 is a power on/off button, via which thesupplementary device 2 may for instance be turned on and off. A secondbutton 33 is a communications button. A third button 34 is a confirm orOK button. The buttons 22, 33, 34 may be any suitable form of mechanicalswitch. These input buttons 22, 33, 34 allow a user to turn on/offsupplementary device 2, to trigger actions (for instance to causeestablishment of a connection to or a pairing with another device,and/or to trigger transmission of information from supplementary device2 to another device), or to confirm something.

FIG. 2c is a schematic illustration of a third embodiment of asupplementary device 2 to be releasably attached to injection device 1of FIG. 1a . Supplementary device 2 comprises a housing 20 with a matingunit configured and embrace the housing 10 of injection device 1 of FIG.1a , so that supplementary device 2 sits tightly on housing 10 ofinjection device 1, but is nevertheless removable from injection device1.

Information is displayed via display unit 21 of the supplementary device2. The dosage window 13 of injection device 1 is obstructed bysupplementary device 2 when attached to injection device 1.

Supplementary device 2 further comprises a touch-sensitive inputtransducer 35. It also comprises a single user input button or switch22. The button 22 is a power on/off button, via which the supplementarydevice 2 may for instance be turned on and off. The touch sensitiveinput transducer 35 can be used to trigger actions (for instance tocause establishment of a connection to or a pairing with another device,and/or to trigger transmission of information from supplementary device2 to another device), or to confirm something.

FIGS. 3A and 3 b show possible distributions of functions among deviceswhen using a supplementary device (such as the supplementary devices ofFIGS. 2a and 2b ) together with an injection device.

In constellation 4 of FIG. 3a , the supplementary device 41 (such as thesupplementary devices of FIGS. 2a and 2b ) determines information frominjection device 40, and provides this information (e.g. type and/ordose of the medicament to be injected) to a blood glucose monitoringsystem 42 (e.g. via a wired or wireless connection).

Blood glucose monitoring system 42 (which may for instance be embodiedas desktop computer, personal digital assistant, mobile phone, tabletcomputer, notebook, netbook or ultrabook) keeps a record of theinjections a patient has received so far (based on the ejected doses,for instance by assuming that the ejected doses and the injected dosesare the same, or by determining the injected doses based on the ejecteddoses, for instance be assuming that a pre-defined percentage of theejected dose is not completely received by the patient). Blood glucosemonitoring system 42 may for instance propose a type and/or dose ofinsulin for the next injection for this patient. This proposal may bebased on information on one or more past injections received by thepatient, and on a current blood glucose level, that is measured by bloodglucose meter 43 and provided (e.g. via a wired or wireless connection)to blood glucose monitoring system 42. Therein, blood glucose meter 43may be embodied as a separate device that is configured to receive asmall blood probe (for instance on a carrier material) of a patient andto determine the blood glucose level of the patient based on this bloodprobe. Blood glucose meter 43 may however also be a device that is atleast temporarily implanted into the patient, for instance in thepatient's eye or beneath the skin.

FIG. 3b is a modified constellation 4′ where the blood glucose meter 43of FIG. 3a has been included into blood glucose monitoring system 42 ofFIG. 3a , thus yielding the modified blood glucose monitoring system 42′of FIG. 3b . The functionalities of injection device 40 andsupplementary device 41 of FIG. 3a are not affected by thismodification. Also the functionality of blood glucose monitoring system42 and blood glucose meter 43 combined into blood glucose monitoringsystem 42′ are basically unchanged, apart from the fact that both arenow comprised in the same device, so that external wired or wirelesscommunication between these devices is no longer necessary. However,communication between blood glucose monitoring system 42 and bloodglucose meter 43 takes place within system 42′.

FIG. 4 shows a schematic view of the supplementary device 2 of FIG. 2ain a state where it is attached to injection device 1 of FIG. 1 a.

With the housing 20 of supplementary device 2, a plurality of componentsare comprised. These are controlled by a processor 24, which may forinstance be a microprocessor, a Digital Signal Processor (DSP),Application Specific Integrated Circuit (ASIC), Field Programmable GateArray (FPGA) or the like. Processor 24 executes program code (e.g.software or firmware) stored in a program memory 240, and uses a mainmemory 241, for instance to store intermediate results. Main memory 241may also be used to store a logbook on performed ejections/injections.Program memory 240 may for instance be a Read-Only Memory (ROM), andmain memory may for instance be a Random Access Memory (RAM).

In embodiments such as those shown in FIG. 2b , processor 24 interactswith a first button 22, via which supplementary device 2 may forinstance be turned on and off. A second button 33 is a communicationsbutton. The second button may be used to trigger establishment of aconnection to another device, or to trigger a transmission ofinformation to another device. A third button 34 is a confirm or OKbutton. The third button 34 can be used to acknowledge informationpresented to a user of supplementary device 2. In embodiments such asthose shown in FIG. 2c , two of the buttons 33, 34 may be omitted.Instead, one or more capacitive sensors or other touch sensors areprovided.

Processor 24 controls a display unit 21, which is presently embodied asa Liquid Crystal Display (LCD). Display unit 21 is used to displayinformation to a user of supplementary device 2, for instance on presentsettings of injection device 1, or on a next injection to be given.Display unit 21 may also be embodied as a touch-screen display, forinstance to receive user input.

Processor 24 also controls an optical sensor 25, embodied as an OpticalCharacter Recognition (OCR) reader, that is capable of capturing imagesof the dosage window 13, in which a currently selected dose is displayed(by way of numbers printed on the sleeve 19 contained in injectiondevice 1, which numbers are visible through the dosage window 13). OCRreader 25 is further capable of recognizing characters (e.g. numbers)from the captured image and to provide this information to processor 24.Alternatively, unit 25 in supplementary device 2 may only be an opticalsensor, e.g. a camera, for capturing images and providing information onthe captured images to processor 24. Then processor 24 is responsiblefor performing OCR on the captured images.

Processor 24 also controls light-sources such as light emitting diodes(LEDs) 29 to illuminate the dosage window 13, in which a currentlyselected dose is displayed. A diffuser may be used in front of thelight-sources, for instance a diffuser made from a piece of acrylicglass. Furthermore, the optical sensor may comprise a lens system, forinstance including two aspheric lenses. The magnification ratio (imagesize to object size ratio) may be smaller than 1. The magnificationratio may be in the range of 0.05 to 0.5. In one embodiment themagnification ration may be 0.15.

Processor 24 further controls a photometer 26, that is configured todetermine an optical property of the housing 10 of injection device 1,for example a colour or a shading. The optical property may only bepresent in a specific portion of housing 10, for example a colour orcolour coding of sleeve 19 or of an insulin container comprised withininjection device 1, which colour or colour coding may for instance bevisible through a further window in housing 10 (and/or in sleeve 19).Information on this colour is then provided to processor 24, which maythen determine the type of injection device 1 or the type of insulincontained in injection device 1 (e.g. SoloStar Lantus with purple colourand SoloStar Apidra with blue colour). Alternatively, a camera unit maybe used instead of photometer 26, and an image of the housing, sleeve orinsulin container may then be provided to processor 24 to determine thecolour of the housing, sleeve or insulin container by way of imageprocessing. Further, one or more light sources may be provided toimprove reading of photometer 26. The light source may provide light ofa certain wavelength or spectrum to improve colour detection byphotometer 26. The light source may be arranged in such a way thatunwanted reflections, for example by dosage window 13, are avoided orreduced. In an example embodiment, instead of or in addition tophotometer 26, a camera unit may be deployed to detect a code (forinstance a bar code, which may for instance be a one- or two-dimensionalbar code) related to the injection device and/or the medicamentcontained therein. This code may for instance be located on the housing10 or on a medicament container contained in injection device 1, to namebut a few examples. This code may for instance indicate a type of theinjection device and/or the medicament, and/or further properties (forinstance a expiration date).

Processor 24 further controls (and/or receives signals from) an acousticsensor 27, which is configured to sense sounds produced by injectiondevice 1. Such sounds may for instance occur when a dose is dialed byturning dosage knob 12 and/or when a dose is ejected/injected bypressing injection button 11, and/or when a prime shot is performed.These actions are mechanically similar but nevertheless sounddifferently (this may also be the case for electronic sounds thatindicate these actions). Either the acoustic sensor 27 and/or processor24 may be configured to differentiate these different sounds, forinstance to be able to safely recognize that an injection has takenplace (rather than a prime shot only).

Processor 24 further controls an acoustical signal generator 23, whichis configured to produce acoustical signals that may for instance berelated to the operating status of injection device 1, for instance asfeedback to the user. For example, an acoustical signal may be launchedby acoustical signal generator 23 as a reminder for the next dose to beinjected or as a warning signal, for instance in case of misuse.Acoustical signal generator may for instance be embodied as a buzzer orloudspeaker. In addition to or as an alternative to acoustical signalgenerator 23, also a haptic signal generator (not shown) may be used toprovide haptic feedback, for instance by way of vibration.

Processor 24 controls a wireless unit 28, which is configured totransmit and/or receive information to/from another device in a wirelessfashion. Such transmission may for instance be based on radiotransmission or optical transmission. In some embodiments, the wirelessunit 28 is a Bluetooth transceiver. Alternatively, wireless unit 28 maybe substituted or complemented by a wired unit configured to transmitand/or receive information to/from another device in a wire-boundfashion, for instance via a cable or fibre connection. When data istransmitted, the units of the data (values) transferred may beexplicitly or implicitly defined. For instance, in case of an insulindose, always International Units (IU) may be used, or otherwise, theused unit may be transferred explicitly, for instance in coded form.

Processor 24 receives an input from a pen detection switch 30, which isoperable to detect whether the pen 1 is present, i.e. to detect whetherthe supplementary device 2 is coupled to the injection device 1.

A battery 32 powers the processor 24 and other components by way of apower supply 31.

The supplementary device 2 of FIG. 4 is thus capable of determininginformation related to a condition and/or use of injection device 1.This information is displayed on the display 21 for use by the user ofthe device. The information may be either processed by supplementarydevice 2 itself, or may at least partially be provided to another device(e.g. a blood glucose monitoring system).

FIGS. 5a-5c are flowcharts of embodiments of methods according to thepresent invention. These methods may for instance be performed byprocessor 24 of supplementary device 2 (see FIGS. 2b and 4), but also bya processor of supplementary device 3 of FIG. 2b , and may for instancebe stored in program memory 240 of supplementary device 2, which may forinstance take the shape of tangible storage medium 60 of FIG. 6.

FIG. 5a shows method steps that are performed in scenarios as shown inFIGS. 3a and 3b , where information read by supplementary device 41 frominjection device 40 is provided to blood glucose monitoring system 42 or42′ without receiving information back from blood glucose monitoringsystem 42 or 42′.

The flowchart 500 starts for instance when the supplementary device isturned on or is otherwise activated. In a step 501, a type ofmedicament, for example insulin, provided by the injection device isdetermined, for instance based on colour recognition or based onrecognition of a code printed on injection device or a component thereofas already described above. Detection of the type of medicament may notbe necessary if a patient always takes the same type of medicament andonly uses an injection device with this single type of medicament.Furthermore, determination of the type of medicament may be ensuredotherwise (e.g. by the key-recess pair shown in FIG. 4 that thesupplementary device is only useable with one specific injection device,which may then only provide this single type of medicament).

In a step 502, a currently selected dose is determined, for instance byOCR of information shown on a dosage window of injection device asdescribed above. This information is then displayed to a user of theinjection device in a step 503.

In a step 504, it is checked if an ejection has taken place, forinstance by sound recognition as described above. Therein, a prime shotmay be differentiated from an actual injection (into a creature) eitherbased on respectively different sounds produced by the injection deviceand/or based on the ejected dose (e.g. a small dose, for instance lessthan a pre-defined amount of units, e.g. 4 or 3 units, may be consideredto belong to a prime shot, whereas larger doses are considered to belongto an actual injection).

If an ejection has taken place, the determined data, i.e. the selecteddose and—if applicable—the type of medicament (e.g. insulin), is storedin the main memory 241, from where it may later be transmitted toanother device, for instance a blood glucose monitoring system. If adifferentiation has been made concerning the nature of the ejection, forinstance if the ejection was performed as a prime shot or as an actualinjection, this information may also be stored in the main memory 241,and possibly later transmitted. In the case of an injection having beenperformed, at step 505 the dose is displayed on the display 21. Alsodisplayed is a time since the last injection which, immediately afterinjection, is 0 or 1 minute. The time since last dose may be displayedintermittently. For instance, it may be displayed alternately with thename or other identification of the medicament that was injected, e.g.Apidra or Lantus.

If ejection was not performed at step 504, steps 502 and 503 arerepeated.

After display of the delivered dose and time data, the flowchart 500terminates.

FIG. 5b shows in more detail exemplary method steps that are performedwhen the selected dose is determined based on the use of optical sensorsonly. For instance, these steps may be performed in step 502 of FIG. 5a.

In a step 901, a sub-image is captured by an optical sensor such asoptical sensor 25 of supplementary device 2. The captured sub-image isfor instance an image of at least a part of the dosage window 13 ofinjection device 1, in which a currently selected dose is displayed(e.g. by way of numbers and/or a scale printed on the sleeve 19 ofinjection device 1, which is visible through the dosage window 13). Forinstance, the captured sub-image may have a low resolution and/or onlyshow a part of the part of sleeve 19 which is visible through dosagewindow 13. For instance, the captured sub-image either shows the numbersor the scale printed on the part of sleeve 19 of injection device 1which is visible through dosage window 13. After capturing an image, itis, for instance, further processed as follows:

Division by a previously captured background image;

Binning of the image(s) to reduce the number of pixels for furtherevaluations;

Normalization of the image(s) to reduce intensity variations in theillumination;

Sheering of the image(s); and/or

Binarization of the image(s) by comparing to a fixed threshold.

Several or all of these steps may be omitted if applicable, for instanceif a sufficiently large optical sensor (e.g. a sensor with sufficientlylarge pixels) is used.

In a step 902, it is determined whether or not there is a change in thecaptured sub-image. For instance, the currently captured sub-image maybe compared to the previously captured sub-image(s) in order todetermine whether or not there is a change. Therein, the comparison topreviously captured sub-images may be limited to the sub-image of thepreviously captured sub-images that was captured immediately before thecurrent sub-image was captured and/or to the sub-images of thepreviously captured sub-images that were captured within a specifiedperiod of time (e.g. 0.1 seconds) before the current sub-image wascaptured. The comparison may be based on image analysis techniques suchas pattern recognition performed on the currently captured sub-image andon the previously captured sub-image. For instance, it may be analyzedwhether the pattern of the scale and/or the numbers visible through thedosage window 13 and shown in the currently captured sub-image and inthe previously captured sub-image is changed. For instance, it may besearched for patterns in the image that have a certain size and/oraspect ratio and these patterns may be compared with previously savedpatterns. Steps 901 and 902 may correspond to a detection of a change inthe captured image.

If it is determined in step 902 that there is a change in the sub-image,step 901 is repeated. Otherwise in a step 903, an image is captured byan optical sensor such as optical sensor 25 of supplementary device 2.The captured image is for instance an image of the dosage window 13 ofinjection device 1, in which a currently selected dose is displayed(e.g. by way of numbers and/or a scale printed on the sleeve 19 ofinjection device 1, which is visible through the dosage window 13). Forinstance, the captured image may have a resolution being higher than theresolution of the captured sub-image. The captured image at least showsthe numbers printed on the sleeve 19 of injection device 1 which arevisible through the dosage window 13.

In a step 904, optical character recognition (OCR) is performed on theimage captured in step 903 in order to recognize the numbers printed onthe sleeve 19 of injection device 1 and visible through the dosagewindow 13, because these numbers correspond to the (currently) selecteddose. In accord to the recognized numbers, the selected dose isdetermined, for instance by setting a value representing the selecteddose to the recognized numbers.

In a step 905, it is determined whether or not there is a change in thedetermined selected dose and, optionally, whether or not the determinedselected dose does not equal zero. For instance, the currentlydetermined selected dose may be compared to the previously determinedselected dose(s) in order to determine whether or not there is a change.Therein, the comparison to previously determined selected dose(s) may belimited to the previously determined selected dose(s) that weredetermined within a specified period of time (e.g. 3 seconds) before thecurrent selected dose was determined. If there is no change in thedetermined selected dose and, optionally, the determined selected dosedoes not equal zero, the currently determined selected dose isreturned/forwarded for further processing (e.g. to processor 24).

Thus, the selected dose is determined if the last turn of the dosageknob 12 is more than 3 seconds ago. If the dosage knob 12 is turnedwithin or after these 3 seconds and the new position remains unchangedfor more than 3 seconds, this value is taken as the determined selecteddose.

FIG. 5c shows in more detail method steps that are performed when theselected dose is determined based on the use of acoustical and opticalsensors. For instance, these steps may be performed in step 502 of FIG.5 a.

In a step 1001, a sound is captured by an acoustical sensor such asacoustical sensor 27 of supplementary device 2.

In a step 1002, it is determined whether or not the captured sound is aclick sound. The captured sound may for instance be a click sound thatoccurs when a dose is dialed by turning dosage knob 12 of injectiondevice 1 and/or when a dose is ejected/injected by pressing injectionbutton 11, and/or when a prime shot is performed. If the captured soundis not a click sound, step 1001 is repeated. Otherwise in a step 1003,an image is captured by an optical sensor such as optical sensor 25 ofsupplementary device 2. Step 1003 corresponds to step 903 of flowchart900.

In a step 1004, an OCR is performed on the image captured in step 1003.Step 1004 corresponds to step 904 of flowchart 900.

In a step 1005, it is determined whether or not there is a change in thedetermined selected dose and, optionally, whether or not the determinedselected dose does not equal zero. Step 1005 corresponds to step 905 offlowchart 900.

There might be a slight advantage of the acoustic approach shown in FIG.5c when it comes to power consumption of the supplementary device,because permanently capturing images or sub-images as shown in FIG. 5btypically is more power consuming than listening to an acoustical sensorsuch as a microphone.

FIG. 6 is a schematic illustration of a tangible storage medium 600 (acomputer program product) that comprises a computer program 601 withprogram code 602. This program code may for instance be executed byprocessors contained in the supplementary device, for instance processor24 of supplementary device 2 of FIGS. 2 and 4. For instance, storagemedium 600 may represent program memory 240 of supplementary device 2 ofFIG. 4. Storage medium 600 may be a fixed memory, or a removable memory,such as for instance a memory stick or card.

As described in detail above, embodiments of the present invention allowconnection of a standard injection device, in particular an insulindevice, with a blood glucose monitoring system in a useful andproductive way.

Embodiments of the present invention introduce a supplementary device toallow for this connection, assuming the blood glucose monitoring systemhas wireless or other communication capabilities. The benefits ofproviding such a supplementary device have been described, for instancein WO 2011/117212.

The term “drug” or “medicament”, as used herein, means a pharmaceuticalformulation containing at least one pharmaceutically active compound,for instance as described in WO 2011/117212.

The mechanical arrangement of the supplemental device 2 and the mannerin which it is attached to the injection device 1 will now be describedwith reference to FIGS. 8 to 14.

As is best seen from FIG. 8, the supplemental device 2 is attached tothe injection pen 1 close to the dosage knob 12 with the display 21uppermost in the orientation shown (which is the same for all of FIGS. 8to 14). The plane of the display 21 lies generally transverse to thelongitudinal axis of the injection device 1, and is perpendicular to thepage of FIGS. 8, 9, 10, 12, 13 and 14.

A closure 68 extends from a shaft 59 of a hinge, the closure extendingunderneath the injection pen. The closure 68 is connected to thesupplemental device 2 on the right side (looking at the injection device1 with the injection button closest to the viewer), extends underneaththe injection pen 1 and connects with the supplemental device on theleft side thereof.

The supplemental device 2 of these illustrated embodiments includes twofeatures that contribute to correct alignment of the supplemental device2 on the injection device 1, and one feature that results in securing ofthe supplemental device 2 to the injection device 1. The features thatcontribute to correct alignment of the supplemental device 2 on theinjection device 1 can be termed alignment arrangements. The featuresthat contribute to securing of the supplemental device 2 to theinjection device 1 can be termed a securing arrangement.

The correct alignment of the supplemental device 2 on the injectiondevice 1, ensures that the OCR reader 25 is correctly aligned with thedosage window 13. Correct alignment allows correct operation andreliable readings. Ensuring that there can be correct alignment betweenthe supplemental device 2 and the injection device 1 in use allows asimpler design for the OCR reader 25, in particular because it does notneed to be designed to be able to accommodate different alignmentsbetween the devices 1, 2.

The first alignment feature is a locating channel 71. The locatingchannel 71 is located at the uppermost part of an injection devicereceiving channel 58 that is defined between the main body of thesupplemental part and the closure 68 when in the closed position.

The locating channel 71 is best shown in FIGS. 11a and 11b . From here,it will be seen that the locating channel is formed at the end of thesupplemental device that is closest to the dosage knob 12 when thesupplemental device 2 is fitted to the injection device 1.

As is best seen in FIG. 1b , the locating rib 70 is located between thedisplay window 13 and the dosage knob 12. In this example, the locatingrib 70 extends for the whole of the distance between the display window13 and the dosage knob 12. In other examples, the locating rib isshorter. The locating rib 70 is taller at the end that is adjacent thedosage knob 12 and tapers down to a zero height at the junction with thedisplay window 13. As can be seen from FIG. 1b , the taper of theuppermost edge of the locating rib 70 is slightly curved. The gradientof the taper is less at the part of the locating rib 70 that is closestto the dosage knob 12 and is greater along the locating rib to thelocation of the display window 13. The shape of the locating rib 70 issuch that the gradient continually increases as one moves from theposition of the locating rib 70 that is adjacent to the dosage knob 12to the position of the locating rib 70 that is adjacent the displaywindow 13.

The thickness of the locating rib 70, the thickness being the dimensionthat is circumferential to the main body of the injection device 1,varies along the length of the locating rib 70. The thickness of thelocating rib 70 is greatest at the end adjacent the dosage knob 12 andis least at the end adjacent the display window 13. The thickness of thelocating rib 70 gradually decreases as one moves from the end of thelocating rib adjacent the dosage knob 12 to the end of the locating ribthat is adjacent the display window 13.

The cross-section of the locating rib, the cross-section being a sectiontaken perpendicular to the longitudinal axis of the injection pen 1, isof a rounded triangle. The cross-section of the locating rib 70 isapproximately the same for its entire length, although of course thesize varies.

The locating channel 71 is dimensioned so as to correspond closely tothe shape and size of the locating rib 70 that is present on theinjection pen 1.

The locating channel 71 has a size and shape that corresponds closely tothe size and shape of the locating rib 70. The locating channel 71 isslightly larger than the locating rib so as to ensure that the locatingrib can be located within the locating channel 71. When the locating rib70 is within the locating channel 71, the corresponding sizes ensurethat the two features mate together. This assists in ensuring correctpositioning of the supplemental device 2 on the injection device 1.

Other features of the supplemental device 2 and the injection pen 1 thatassist in ensuring correct alignment between the two devices will now bedescribed. As best seen in FIG. 1b , the injection pen 1 is providedwith indents on either side of its body at locations close to the dosageknob 12. In FIG. 1b , a left side indent 52 is shown. A right indent 51,which is shown in FIGS. 10 and 12, is located in a correspondingposition on the right side of the injection pen 1.

The left and right indents 51, 52 are relatively shallow depressions.The indents 51, 52 have sloping sides, that is the sides of the indents51, 52 are not parallel. Also, they are not radial with respect to thelongitudinal axis of the injection pen 1. In these embodiments, theslope of the sides of the left and right indents 51, 52 is different fordifferent parts of the indents. In particular, the gradient of the slopeof the sides of the indents is less at the part of the indents that isfurthest from the display window 13 and is greatest at the part of theindents 51, 52 that is closest to the display window 13. In theseexamples, the slope of the indents changes between these two extremes,for instance in a linear fashion.

The slope of the sides of the indent may for instance be between 30 and70 degrees at the part that is furthest from the display window 13. Theslope may for instance be between 60 and 80 degrees for the part that isclosest to the display window 13. The greater angle of slope at the partcloser to the display window 13 aids engagement of a face of aprotuberance within the indent 51, 52 in such a way as to provide someresistance against removal of the supplemental device 2 in a directionradial to the longitudinal axis of the injection device 1.

As is best seen in FIGS. 10 and 11, the left and right protuberances 53,54 are shaped to correspond to the shapes of the right and left indents51, 52 respectively. In this way, the right and left protuberances 53,54 fit within the right and left indents 51, 52 respectively when thesupplementary device 2 is correctly positioned on the injection pen 1.The external dimensions of the right and left protuberances 53, 54 areslightly smaller than the internal dimensions of the right and leftindents 51, 52 so as to ensure that the protuberances fit within theirrespective indent.

In these embodiments, the left and right protuberance 52 is shaped tocorrespond closely to the shape of the right indent 51. In this way, theright protuberances 53 fits snugly within the right indent 51 when thesupplementary device 2 is correctly positioned on the injection pen 1.The left protuberance 54 is shaped similarly to the right protuberance53, although it is less tall. Put another way, it is like the rightprotuberance 53 but with the top part missing or cut off. This is thereason for the end face of the left protuberance 54 having a larger areathan the right protuberance 53. The different sizes for theprotuberances 53, 54 helps the protuberances find engagement within theindents 51, 52. The right protuberance 53 can be consider to be a masterto the left protuberance, which is a slave.

The right protuberance 53 is located at the end of the right arm 55,which is best shown in FIG. 11 b.

As can be seen from FIG. 11a , the left protuberance 54 is located atthe end of the left arm 56.

As can be best seen from FIG. 10, the right and left arms 55, 56 dependsubstantially vertically from the body 20 of the supplementary device 2.The right and left arms 55, 56 are thus formed either side of theinjection device receiving channel 58.

A biasing feature 67, in the form of a u-shaped spring, is coupled toeach of the right and left arms 55, 56. The effect of the spring 67 isto bias the right and left arms into a certain position. The positioninto which the right and left arms 55, 56 are biased is such that thedistance between the innermost surfaces of the right and leftprotuberances 53, 54 is slightly less than the distance between thebottoms of the right and left indents 51, 52. The effect of the spring67 is to resist movement of the protuberances 53, 54 and the arms 55,56, away from one another.

Because the slopes of the sides of the protuberances 53, 54 match thesides of the indents 51, 52, the sloped sides of the protuberances 53,54 at the distal ends of the arms 55, 56 is relatively shallow. Thisassists in sliding the protuberances 53, 54 over the external surface ofthe body 10 of the injection pen 1 as the supplemental device is beingfitted. This is best demonstrated with reference to FIGS. 10 and 12.

As is shown in FIG. 10, the supplemental device 2 is located withrespect to the injection pen 1 such that the ends of the right and leftarms 55, 56, in particular the protuberances 53, 54, are just touchingthe housing 10 of the injection pen 1. The protuberances 53, 54 herecontact the housing to the left and right sides of the display window13.

The left and right arms 55, 56 are present behind flaps 60 that dependfrom the supplemental device 2 on both the left and right sides. As canbe seen from FIG. 10, the flaps, or protecting walls 60, extend slightlyfurther in a downwards direction than the arms. The flaps 60 are formedof transparent material. This allows a user to be able to view thelocations of the arms 55, 56 relative to the indents 51, 52, which mayhelp them to locate the supplemental device 2 correctly on the injectiondevice 1. FIG. 8 shows the location of the left indent 52 in dottedform, to highlight the location of the arms, 55, 56 as well as theindents 51, 52, although the arms are not shown in this view.

In order to mate the supplemental device 2 with the injection device 1,the user first arranges the supplemental device 2 with respect to theinjection device 1 as shown in FIG. 10, and then applies a forcedownwards on the supplemental device 2 while at the same time applying aforce upwards on the injection device 1. This places force on theprotuberances 53, 54, and thus the right and left arms 55, 56. As theinjection device 1 and the supplemental device 2 move closer together,the force results in the arms being moved apart, against the resilienceof the spring 67. This causes the spring 67 to apply a reaction force,which resists entry of the injection device 1 into the injection devicereceiving channel 58. However, when the protuberances 53, 54 reach thelocation on the injection pen 1 at which they are directly in line withthe longitudinal axis of the injection device 1, the reaction forcesupplied by the spring 67 ceases to increase upon further movement ofthe injection device 1 and the supplemental device 2 together. Afterthis point, the movement of the injection pen 1 into the injectiondevice receiving channel 58 is aided by the resilience of the spring 67.

After some further movement, the protuberances 53, 54 become alignedwith the left and right indent 51, 52 and, due to the resilience of thespring 67, become engaged with the indents. Engagement provides hapticand audio feedback as the protuberances 53, 54 click or snap into theindents 51, 52. The feedback is enhanced by the force provided by theresilience of the spring 67. Once the protuberances 53, 54 are matedwith the indents 51, 52, there is significant resistance to furthermovement of the supplemental device 2 relative to the injection device1, due in part to the corresponding shapes of the protuberances 53, 54and the indents 51, 52 and due in part to the biasing together of thearms 55, 56 by the spring 67.

If when the supplemental device 2 and the injection device 1 are movedtogether one of the indents 51, 52 is higher than the other, one of theprotuberances 53, 54 will engage with the higher one of the indentsbefore the other one of the protuberances reaches the other indent. Inthis case, the protuberance and indent that first meet become engaged,and present significant resistance to further movement of thatprotuberance relative to that indent. In this case, the tendency isnaturally for the injection device 1 to be rotated relative to thesupplemental device such that the other indent meets the otherprotuberance. Once the other indent meets the other protuberance, theymate together and considerable resistance is presented against furthermovement of the injection pen 1 relative to the supplemental device 2.In the scenario in which one of the protuberances meets an indent beforethe other protuberance meets its respective indent, the experience ofthe user is such that the injection pen 1 and the supplemental device 2seem to move together initially with little or no rotation. Haptic andaudio feedback is then provided when the first protuberance meets thecorresponding indent, and after this point the injection device 1 seemsto roll into place within the injection device receiving channel 58until the other protuberance is received in the other indent, at whichpoint further haptic and audio feedback is provided to the user.

Once the protuberances 53, 54 are mated in the indent 51, 52, theinjection device 1 is fully located within the injection devicereceiving channel 58 as shown in FIG. 12. Here, it will be seen that theoutermost surface of the display window 13 is generally aligned with alowermost surface of the upper part of the supplemental device 2. Thissupplemental device 2 is shaped such that the injection device 1 fitssnugly within the injection device receiving channel 58 and there aremultiple points or areas of contact between the exterior surface of thehousing 10 of the injection device 1 and the lowermost surface of thesupplemental device 2 when the supplemental device and the injection pen1 are in this relative position. Even in the absence of the mating ofthe protuberances 53, 54 with the indents 51, 52 at this point, the userwould notice that there is a natural tendency for the injection pen 1 tosit at this location within the supplemental device 2.

When the supplemental device 2 is located with respect to the injectionpen 1 such that the right and left protuberances 53, 54 are locatedwithin the right and left indents 51, 52 respectively, the locating rib70 is engaged within the locating channel 71. Correct alignment of thesupplemental device 2 with respect to the injection device 1 is thusprovided in two ways: firstly, by the location of the locating rib 70within the locating channel 71 and secondly by the locating of theprotuberances 53, 54 within the indents 51, 52.

In the event that the user places the supplemental device 2 onto theinjection pen 1 at a location such that the supplemental device 2 isslightly at the right of the position shown in FIG. 8, the locating rib70 does not fit within the locating channel 71. In this case, thesupplemental device 2 is prevented from being located fully over theinjection pen 1 by the locating rib 70 resting against a surface of thesupplemental device 2 that is in some way distal from the correctlocation within the locating channel 71. However, in this position, theends of the protuberances 53, 54 have passed the halfway point of thecircumference of the housing 10 of the injection device 1 and thus thespring 67 results in the injection device 1 being biased towards thesupplemental device 2 so as to be located within the injection devicereceiving channel 58. A user would know that the supplemental device 2had not mated correctly with the injection pen 1 because they would nothave received any haptic feedback from the mating of the protuberances53, 54 with the indents 51, 52. They would also notice that the end ofthe supplemental device that is closest to the dosage knob 12 wasseparated from the injection pen 1 by a distance greater than theseparation of the supplemental device 2 from the injection pen 1 at theend of the supplemental device 2 distal from the dosage knob 12. In thissituation, the user can engage the supplemental device 2 and theinjection pen 1 simply by exerting a force against the supplementaldevice 2 and the injection pen 1 such as to move the supplemental device2 leftwards in the direction shown in FIG. 8. This can be achieved in aone-handed fashion or in a two-handed fashion. As the supplementaldevice 2 and the injection device 1 move relative to one another, thelocating rib and the locating channel become more and more engaged. Thespring force provided by the spring 67 may assist relative movement ofthe supplemental device 2 and the injection device 1 in this manner. Asthe locating rib 70 and the locating channel 71 become more engaged, theend of the supplemental device 2 that is closest to the dosage knob 12moves down towards the injection device 1. This movement continues untilthe locating rib 70 is completely within the locating channel 71, atwhich point the right and left protuberances 53, 54 also engage with theright and left indents 51, 52 respectively. At this point, hapticfeedback is provided by the mating of the protuberances 53, 54 with theindents 51, 52 and the user can determine that the supplemental device 2and the injection device 1 are properly located with respect to oneanother.

If the user locates the supplemental device onto the injection pen 1such that the supplemental device is to the left of the position shownin FIG. 8, mating between the supplemental device 2 and the injectionpen 1 will not occur. In this case, the locating rib 70 will not preventthe supplemental device 2 from being located flat against the injectionpen 1. A user, noticing this, will know that the supplemental device 2is located too far from the dosage knob 12. The user can engage thesupplemental device 2 with the injection pen 1 simply by moving thesupplemental device 2 relative to the injection device 1 such as to movethe supplemental device 2 rightwards in the direction shown in FIG. 8.

If the locating rib 70 is aligned with the locating channel 71 when theend of the locating rib 70 that is closest to the display window 13, thesmallest end of the locating rib 70 will enter the mouth, being thelarge open end, of the locating channel 71. At this stage, thesupplemental device still is located against the surface of theinjection device 1, with the injection device 1 being fully locatedwithin the injection device receiving channel 58. Because of the actionof the spring 67, the injection device 1 is biased into the injectiondevice receiving channel 58 against the supplemental device 2 at thisstage.

If the locating rib 70 and the locating channel 71 are not exactlyaligned, the narrowest end of the locating rib 70 will engage with aside of the locating channel. Further relative movement of thesupplemental device 2 and the injection device 1 in a longitudinaldirection results in a reactive force being applied between the locatingrib and a wall of the locating channel 71, biasing the supplementaldevice 2 and the injection device 1 towards being in full alignment.This occurs until the locating rib 70 is fully engaged within thelocating channel 71, at which point the right and left protuberances 53,54 also engage with the right and left indents 51, 52. At this point,the supplemental device 2 and the injection device 1 are fully engagedwith one another.

The supplemental device 2 is provided with a closure 68, which has aprimary function of clamping the supplemental device 2 to the injectionpen 1 when the two devices are mated with one another.

As best seen in FIGS. 13 and 14, the closure 68 has an innermost surfacethat coincides with the curved surface of an imaginary cylinder. Thediameter of the cylinder is the same as the external dimension of thehousing 10 of the injection device 1. As such, the closure 68 forms asnug fit against the lowermost part of the housing 10 of the injectiondevice 1 when the supplemental device 2 is in place on the injectiondevice 1.

The closure 68 is moveable between an open position, shown in FIG. 13,and a closed position, shown in FIG. 14.

As can be seen in FIG. 8, the closure 68 is located next to the armprotecting walls 60, in a direction opposite the arm protecting walls 60to the dosage knob 12. The closure 68 has a dimension in a longitudinalaxis of the injection pen 1 that is approximately 60% of the lengthdimension of the supplemental device 2. In other examples, the length ofthe closure 68 in a longitudinal direction of the injection pen 1 maytake a value anywhere between 30 and 80% of the length of thesupplemental device 2, and preferably between 40 and 70% of the lengthof the supplemental device 2.

The material of the closure 68 has a generally uniform thickness. Assuch, the external surface of the closure 68, that is the surface thatis furthest from the longitudinal axis of the injection pen 1 when thesupplemental device 2 is mated with the injection pen 1, is generallycylindrical, or at least takes the form of part of a cylinder.

The closure 68 is provided with two cutaways 72, 73. The cutaways 72, 73extend from an edge of the closure 68 that is furthest from the shaft 59of the hinge formed at the other side of the supplemental device 2. Thecutaways 72, 73 extend from this edge in a direction that is generallycircumferential with respect to the injection pen 1. The length of thecutaways is approximately equal to ⅙ or ⅕ of the circumference of thecircle on which the closure 68 generally lies. The cutaways 72, 73define a tab 61. The tab 61 is connected to the main part of the closure68 at a location between the lowermost ends of the cutaways 72, 73. Afree end 63 of the tab 61 is located between the uppermost ends of thecutaways 72, 73. As is best seen in FIG. 9, the free end 63 of the tab61 is curved so as to extend away from the longitudinal axis of theinjection pen 1 by a greater extent at a point that is central betweenthe cutaways 72, 73. This allows a user better to be able to locate adigit on the free end 63 of the tab 61 so as to be able to pull the freeend 63 in a direction that is downwards and leftwards in FIG. 14.

On the inside surface of the tab 61 is provided a latching edge 64,which is best seen in FIGS. 9, 13 and 14. The latching edge 64 isprovided at a junction between a latching face and another face. Thelatching edge 64 extends for the width of the tab 61. The latching faceis in a plane that extends approximately radially with respect to thelongitudinal axis of the injection 1 when the closure 68 is in theclosed position, as shown in FIG. 14. In this position, the latchingedge 64 is engaged with a latch engaging face 66 that is provided as apart of the uppermost portion of the supplemental device 2, i.e. isprovided as a portion of the supplemental device 2 that is not part ofthe closure 68. The latch engaging face 66 is provided in a plane thatis generally the same orientation as the plane of the latching face whenthe closure 68 is in the closed position.

When the user has mated the supplemental device 2 onto the injection pen1, in particular mating the locating rib 70 within the locating channel71 and locating the protuberances 53, 54 within the indents 51, 52, theuser may secure the supplemental device 2 to the injection pen 1. Thisis achieved by the user moving the closure 68 from the position shown inFIG. 9, in which the injection device receiving channel 58 is open forinclusion of the injection pen 1 therein, and rotating the closure 68around the shaft 59 of the hinge so as to move the free end 63 of thetab 61 towards the latch engaging face. Movement continues until contactis made between the innermost part of the latching edge 64 against aguide surface 65, which is located just beneath (as shown in theFigures) the latch engaging face 66. The guide surface 65 is angledapproximately tangentially to the outside surface of the housing 10 ofthe injection pen 1.

At this point, the tendency of the closure 68 to adopt the shape shownin FIG. 13 provides a spring force between the end of the tab 61 and theguide surface 65. As the user exerts further force against the closure68, the closure 68 deforms resiliently so as to increase the separationbetween the free end 63 of the tab 61 and the hinge 59. This allows theedge of the latching edge 64 to slide over the guide surface 65. Thiscontinues until the latching edge 64 becomes aligned with the edgebetween the guide surface 65 and the latch engaging face 66, at whichpoint the latching edge 64 and the latching face engage within thechannel that is formed against the latch engaging face 66. At thispoint, the resilience of the closure 68 results in the latching edge 64and the latch engaging face 66 becoming engaged with one another, and atthis point the components are in the position shown in FIG. 14. In thisposition, it will be seen that the innermost surface of the closure 68is snug against the outermost surface of the housing 10 of the injectionpen 1. At this point, the closure 68 ensures that the injection pen 1 istightly contained within the injection device receiving channel 58 andis held in place by the closure 68.

It will be appreciated that this arrangement prevents movement of theinjection device 1 relative to the supplemental device 2 in the plane ofFIG. 14.

Movement of the supplemental device 2 along the longitudinal axis of theinjection pen 1 is inhibited by the mating between the protuberances 53,54 and the indents 51, 52. Additionally, movement of the supplementaldevice 2 in a rightwards direction as shown in FIG. 8 is furtherprevented by the locating rib 70 acting against the body 20 of thesupplemental device 2.

In some embodiments, the locating rib 70 and the locating channel 71 areabsent. In these embodiments, the correct alignment between thesupplemental device 2 and the injection pen 1 is provided by mating ofthe protuberances 53, 54 and the indents 51, 52.

In some other embodiments, the right and left arms 55, 56 and theprotuberances 53, 54 are absent. In these embodiments, the correctalignment between the supplemental device 2 and the injection device 1is provided by the locating rib 70 and the locating channel 71.

Of course, other alternative arrangements for ensuring a correctrelative position between the supplemental device 2 and the injectionpen 1 will be envisaged by the skilled person, and all such alternativesare within the scope of the invention except when explicitly excluded bythe language of the claims.

Also, the skilled person will be aware of alternative securingarrangements, for instance clamping, the supplemental device 2 to theinjection pen 1 once the correct relative position has been attained.Such alternatives include various other latching mechanisms involving aresilient component, such as a tab or an arm, and no complicated movingparts. Other such embodiments involve more complicated moving parts, forinstance clamps with twist-to-lock mechanisms, tension clips and othersuch mechanisms. A hinge is a relatively simple way of connecting themain body of a supplemental device with a closure part, althoughalternative connection arrangements will be envisaged by the skilledperson. Suitable connection arrangements may include slide mechanisms,clips, etc.

FIG. 15 is a cross-sectional view through the supplemental device 2 andthe injection pen in a direction perpendicular to the axis of theinjection pen 1. The cross-section is through the OCR reader 25, whichis in the form of a camera. The camera 25 may also be called a sensor.FIG. 15 is not a true cross section in that third and fourth LEDs 29 d,29 c, which are beyond the cross-section, are visible.

In FIG. 15 it can be seen that the dosage window 13 is of even thicknessin cross-section and has a shape that forms part of a cylindricalannulus. The axis of the cylinder on which the dosage window 13 falls isthe axis of the injection pen 1. The dosage window 13 may be slightlyconical in the axial direction.

In FIG. 15, the supplemental device 2 is engaged with the injection pen1, forming a snug fit therewith. Moreover, the supplemental device 2 andthe injection pen 1 are aligned correctly, by virtue of the mating ofthe protuberances 53, 54 in the indents 51, 52 and the mating of thealignment rib 70 and the alignment channel 71. In this position, thecamera 25 is directed at the dosage window 13.

Interposed between the camera 25 and the dosage window 13 is aprotection window 80. The window 80 is shown in FIG. 16 and FIG. 18also. As best seen from FIG. 15, the protection window 80 includes alowermost surface that falls on the curved surface of a cylinder havingan axis aligned with the axis of the injection pen 1. The uppermostsurface of the protection window 80 has a smaller radius. Thus, theprotection window 80 has a greater thickness at its central part, whichis in the path directly between the camera 25 and the axis of theinjection pen 1, than it does at its edges. Thus, the protection window80 has optical power. The protection window 80 is configured such thatit forms part of the imaging system of the camera 25, along with thelens 25 a. The lens 25 s in these embodiments has two lenses, referredto as a lens for ease of explanation. The optical power of theprotective window 80 can be seen also in the end view of the FIG. 16aand in the cross-section of FIG. 16b . The optical power of theprotection window 80 allows a short track length and contributes to acompact arrangement.

The protection window 80 may be formed of any suitable opticallytransparent material. For instance, the protection window is formed ofoptics grade plastics, for instance optics grade polycarbonate or PMMA(polymethyl methacrylate acrylic).

At the left edge of the window 81 is provided a feature that connectswith a left window support 83 that forms part of the body 20 of thesupplemental device 2. A feature 82 on the right edge of the window issimilarly configured to rest against a right window support 84 thatforms part of the body 20 of the supplemental device 2. The left andright window supports 83, 84 serve to support the protection window 80in a correct location with respect to other components of thesupplemental device 2. The protection window 80 includes features at theleft and right ends of the window, as shown in FIG. 16b , that serve toallow mechanical coupling with features of the supplemental device 2 andwhich are not relevant to the optical system, so are not described here.

The protection window 80 is sealed with respect to the body. Thisprevents the ingress of dirt, dust and other debris into the body 20 andthus helps to maintain correct operation of the camera 25 and otherparts of the optical system. Thus, the protection window 80 forms partof the mechanical configuration of the body 20 of the supplementaldevice as well as part of the optical system. This helps to allowcompactness in the overall arrangement.

As is best seen in FIG. 1a , the dosage window 13 is not square withrespect to the injection pen 1. Instead, the dosage window is at anangle, which allows the dosage sleeve 19 to provide numbers in a helicalfashion, the numbers appearing in the dosage window 13 as the dosagedial 12 is rotated by a user and a dose is delivered. In the SoloStarinjection pen produced by Sanofi, the dosage window 13 and the markingson the dosage sleeve 19 are inclined at 13 degrees.

As can be best seen from FIGS. 17 and 18, the optical arrangementcomprising the camera 25 and the first to fourth LEDs 29 a-29 d areskewed with respect to the main axis of the injection device 1. Theoptical components are skewed to be aligned with the skewed lumbersleeve 19 and dosage window 13. In the case of a SoloStar injection pen,the amount of skew is 13 degrees.

As best seen from FIG. 17 and FIG. 18, the first to fourth LEDs 29 a-29d are separated from the lens 25 a of the camera 25. In this example,they are distributed around the lens 25 a. The LEDs 29 a-29 d areconfigured to illuminate the dosage sleeve 19, so that markings on thedosage sleeve can be read by the camera 25. As can be seen best fromFIG. 15, the LEDs 29 a-29 d are angled or tilted towards the centre ofthe dosage window 13. This provides more effective illumination of thedosage sleeve 19 and can improve overall efficiency of the illumination.

The field of view of the camera 25 covers the whole width of the dosagesleeve 19. The field of view of the camera 25 also covers a sufficientpart of the length of the dosage field 19 that markings provided on thedosage sleeve are captured by the camera 25 during operation.Illumination from the first to fourth LEDs 29 a-29 d passes through theprotection window 80 and the dosage window 13 of the injection pen 1 toilluminate the dosage sleeve 19, on which dose number markings arepresent. The camera 25 is arranged to view the dosage sleeve 19, takinginto account refraction caused by the protection window 80 and thedosage window 13. As mentioned, the protection window 80 is part of theimaging system of the camera 25.

The LEDs 29 a-29 d are arranged so as to achieve substantially uniformillumination of the dosage sleeve. This is achieved by using LEDs 29a-29 d with substantially uniform illumination patterns within definedangular and spatial ranges. The LEDs 29 a-29 d are positioned so that,taking into account the optical effects of the protection window 80 andthe dosage window 13, a uniform illumination pattern is obtained at thedosage sleeve 19.

Each of the first to fourth LEDs 29 a-29 d illuminates a portion of thedosage sleeve 19 including the whole of the quadrant of the dosagesleeve 19 that is closest to the respective LED 29 and including thecentre point of the dosage sleeve 19, which is directly beneath thecamera lens 25 a. In some embodiments, each of the LEDs 29 mayilluminate only their respective quadrant and extend slightly intoneighbouring quadrants. In other embodiments, each of the LEDs 29illuminates a greater proportion of the dosage sleeve. For instance,each LED may illuminate more than 60%, more than 70% or more than 80% ofthe dosage sleeve. The greater the area illuminated by each of the LEDs29, the better is the illumination of the dosage sleeve 19.

Each of the LEDs 29 is positioned relatively distant from the cameralens 25 in the plane of the camera lens. The LEDs 29 lie approximatelyin the plane of the camera lens 25 a, although as can be seen in FIG. 15in this particular example the LEDs 29 lie slightly below the plane ofthe camera lens 25 a. This contributes to the compactness of thesupplemental device 2. It also prevents the absorbing of light throughother device features such as a barrel of the camera lens 25 a. Thus,also it contributes to better homogeneity and overall brightness level.

As can be seen from FIG. 17, the first to fourth LEDs 29 a-29 d are notlocated directly above the dosage window 13. Instead, they are locatedslightly to the side. This does not affect the optical arrangementbecause the LEDs 29 a-29 d have illumination patterns that extendtowards the dosage window 13.

In other embodiments, the LEDs are not tilted and instead all radiate ina common direction from the plane in which they lie. In furtherembodiments, a light guide with outcoupling features is used. This canprovide a more even illumination.

As can be best seen from FIG. 18, the protection window 80 extendsbetween the LEDs 29 a-29 d and the dosage window 13. The protectionwindow 80 covers all or substantially all of the area of the dosagewindow 13.

The LEDs 29 and the protection window 80 are arranged such that lightpaths meet boundaries between air and optical components at angles thatare less than the angle of total internal reflection for the boundary.The protection window 80 is formed of a material that reflectsrelatively little light that is incident at angles less than the angleof total internal reflection.

For a given one of the LEDs 29 a-29 d, there will be a point on thelowermost surface of the dosage window 13 at which light could reflectdirectly onto the camera. For each LED 29, there is also a point on theuppermost surface of the dosage window at which light could reflectdirectly onto the camera 25. This reflected light can be termed reflex.Reflexes from the lowermost surface of the dosage window 13, which isthe surface closest to the dosage sleeve 19, are more relevant tocorrect imaging by the camera 25. Reflexes are experienced because thedosage window 13 is not coated with a non-reflective coating. The dosagewindow 13 may be made of relatively low-cost polycarbonate, whichusually has relatively reflective surfaces.

On the lowermost surface of the dosage window 13, there is a point wherelight from the fourth LED 29 d would reflect to the camera lens 25 a.This point may be termed the reflection point of the fourth LED 29 d. Atthe reflection point of the fourth LED 29 d, light from the LED 29 d haspassed through one boundary from air into the material of the protectivewindow 80 and through another boundary from the material of theprotective window 80 to air. Because the protective window 80 has anoptical power, the direction of incidence of a ray of light on theuppermost surface of the dosage window 13 is different from thedirection of the same ray when it left the fourth LED 29 d. Lightarriving at the uppermost surface of the dosage window 13 is refractedagain by the boundary between air and the dosage window 13 and continuestowards the lowermost surface of the dosage window 13. From thereflection point of the fourth LED 29 d, reflected light would berefracted at three boundaries provided by the uppermost surface of thedosage window 13 and the two surfaces of the protection window 80 beforearriving at the camera lens 25 a. As such, and because the protectionwindow 80 has an optical power and because of refraction provided at theuppermost surface of the dosage window 13, the direction of travel ofthe reflected ray leaving the lowermost surface of the dosage window 13is different to the direction of travel of the ray when it is incidenton the camera lens 25 a.

The reflection point for the fourth LED 29 d is one where a first lineperpendicular to the lowermost surface of the dosage window 13 lies in afirst plane in which the light incident from the fourth LED 29 d and thelight reflected to the camera lens 25 a also lie, and in which an anglefrom the first line to a second line that connects the light incidentfrom the fourth LED 29 d to the reflection point is the same as an anglefrom the first line to a third line that connects the reflection pointto the light passing to the camera lens 25 a.

There are two main sections to the central window part of the protectionwindow 80, which will now be described with reference to FIG. 16d . Themain sections will be referred to as a central portion and a peripheryportion. The central portion is indicated by Rx and the peripheryportion is indicated by Ry. The central portion Rx has a differentoptical power than the periphery portion. In these embodiments, thesurface of the protection window 80 that is closest to the dosage windowin use has a constant radius and the radius of the surface on the sideof the protection window 80 that is closest to the camera 25 isdifferent for the central portion Rx and the periphery portion Ry.However the converse may be true or there may be different radii on bothsurfaces. Here, Rx indicates the central portion and also indicates theradius of the surface closest to the sensor 25, and Ry indicates theperiphery portion and also indicates the radius of the surface closestto the sensor 25.

Most or all of the central portion Rx lies on the optical path betweenthe sensor 25 and the area of interest of the sleeve 19 that is visiblethrough the dosage window 13. The periphery portion Ry does not lie onthe optical path between the sensor 25 and the area of interest of thesleeve 19 that is visible through the dosage window 13. However, some orall of the periphery portion Ry does lie on the optical path between thelight sources 29 and the area of interest of the sleeve 19 that isvisible through the dosage window 13. Consequently, the central portionRx is part of the optical imaging system for reading the numbers visibleon the part of the sleeve 19 that is visible in the dosage window 13,and the periphery portion Ry is not part of this optical imaging system.However, the periphery portion Ry is part of the optical system by whichillumination of the sleeve 19 that is visible through the dosage window13 by the light sources 29 is achieved. At least some of the centralportion Rx also is part of this optical illumination system.

The central portion Rx forms a convex lens, which has a greaterthickness at its centre than it does at its periphery. The peripheryportion Ry may have no optical power at all, in that it may not convergeor diverge incident light. Thus the central portion Rx and the peripheryportion Ry have different optical powers.

The shape of the central portion Rx has an effect of reducing pincushion distortion, as is described below. This is not true of theperiphery portion Ry for two reasons: firstly, it has no optical powerand secondly it is not part of the imaging optical path. However, theperiphery portion Ry does assist in providing even illumination of thesleeve 19 by the light sources 29. This results because of the locationof the periphery potion Ry in the optical illumination path between thelight sources 29 and the sleeve 19 and because the periphery portion Ryis optically sound.

The provision of the periphery portion Ry with lower optical power thanthe central portion Rx (e.g. zero optical power compared to negativepower) allows the protection window 80 to be formed with less materialthan would be possible if the same optical power was applied across thewhole width dimension of the protection window. This can reduce the costand weight of the supplemental device 2. Moreover, the thickness of thecentre of the protection window 80 is lower, for a given radius Rx and agiven width of protection window 80, which can contribute to a morecompact arrangement. The thickness of the material at the peripheryportion Ry dictates the mechanical strength of the protection window 80and is chosen such that the protection window 80 has a suitablemechanical strength.

In the absence of the central portion Rx of the protection window 80 asdescribed above, the output of the camera 25 would experience pincushion distortion. In the particular arrangement shown, there are twosources for the pin cushion distortion. The first is the optical systemof the camera 25 and its lens 25 a in conjunction with the dosage window13. Pin cushion distortion results from the optical system in part fromthe short track length, i.e. the short distance between the camera 25and the dosage window 13, and in part from the shape of the lens 25 s.Secondly, pin cushion distortion results also from the curved shape ofthe sleeve 19. The pin cushion distortion that would be experienced inthe absence of the central portion Rx of the protection window 80 isshown in FIG. 19a . This is the output of a camera viewing an evenrectangular grid of squares. It will be seen that the grid is notrectangular in the camera output, but is pin cushion shaped.

The output of the same camera in the same situation but with theprotection window 80 in place with the central portion Rx in the imagingoptical path is shown in FIG. 19b . Here, it will be seen that the pincushion distortion is significantly reduced, although still present tosome degree.

Removal or reduction of pin cushion distortion is advantageous becauseit allows better performance by the OCR system 25. In particular,performance is better because the numerals/characters on the sleeve 19in the dosage window 13 are more reliably detected by the OCR system 25and/or are detected using fewer processing resources. Using fewerprocessing resources reduces power consumption. More reliablenumeral/character detection results in improved operation of thesupplemental device 2 and an improved user experience.

There are two main alternatives for the shape of the optical part of theprotection window 80.

In a first alternative, the surface of the protection window 80 that isclosest to the sensor 25 has a cylindrical shape. Because the surface ofthe protection window 80 that is closest to the sleeve 19 is alsocylindrical, in this alternative the protection window 80 has a constantthickness along its length, which is the dimension shown in crosssection B-B of FIG. 16f . This applies particularly to the centralportion Rx, but it also applies to the periphery portion Ry. In thefirst alternative, the central portion Rx forms a cylindrical lens.

In a second alternative, the central part Rx of the protection window 80is toric, and forms a toric lens. In this alternative, the protectionwindow 80 has a thickness that is greatest at a point at or close to themiddle part along its length, which is the dimension shown in crosssection B-B of FIG. 16f , and tapers to lower thicknesses at distancesfurther from the point where it has the greatest thickness.Advantageously the surface of the protection window 80 that is closestto the sleeve 19 is cylindrical and the surface that is closest to thecamera 25 is curved, but the converse may be true or both surfaces maybe curved in the length direction. This applies only to the centralportion Rx; the periphery portion Ry does not have a toric lens shape.

A cylindrical lens, according to the first alternative, is simpler tomake than a toric lens. The ability to remove pin cushion distortion issimilar for a toric lens as for a cylindrical lens.

The transition between the central portion Rx and the periphery portionRy may be a step transition, or it may be graded over a short distance.A step transition may provide better optical performance, but a gradedtransition may be simpler to manufacture.

The protection window 80 is formed of an optical plastic, for instancepolycarbonate. This allows the protection window 80 to be made at lowcost whilst allowing the optical imaging system to function correctly(other materials have inferior optical properties and could reduce theeffectiveness of the optical imaging system).

However, the use of optical plastic can introduce optical reflexes,which would reduce the effectiveness of the optical imaging system.Optical reflexes result from the refractive index variation from air.This is mitigated in the present embodiments through the application ofan anti-reflective coating on the protection window 80. Theanti-reflective coating may be applied to the surface that is closest tothe camera 25. It may alternatively be provided to the surface that isclosest to the sleeve 19. Alternatively, it may be applied to both ofthese surfaces.

By using an anti-reflective coating consisting of relatively fewdielectric single layers, the coating can be made to be very stableunder common environmental conditions. Here, the anti-reflective coatingmay consist of between three and five dielectric single layers. Theshape of the reflective spectrum of this type can be described as aV-form spectrum.

Various alternatives will be apparent to the skilled person and all suchalternatives are within the scope of the invention unless excluded bythe scope of the claims.

For instance, instead of LEDs, any other suitable light sources may beused. Suitable light sources may include light bulbs, laser diodes andorganic LEDs.

Although four light sources are included in the shown embodiments, inother embodiments there are one, two, five or more than five lightsources. The choice of the number of light sources may depend on theparticular light source type chosen, brightness, efficiency and costrequirements.

Also, although the protection window 80 is located close to the dosagewindow 13 when the supplemental device 2 is in position on the injectionpen 1 in the embodiments above, they may instead be separated by asignificant distance. Providing the protection window 80 close to thedosage window 13 contributes to providing a compact arrangement. Theprovision of a compact arrangement is assisted by the provision of theprotection window 80 as described above.

The invention claimed is:
 1. A supplemental device for attachment to aninjection device including a dosage window covering a sleeve on whichdose values are marked, the supplemental device comprising: a main body;an arrangement for supporting the main body of the supplemental devicein a predetermined positional relationship with the injection device; atransparent protection window located at a surface of the main body thatis aligned with the dosage window of the injection device when in use;and a sensor arrangement supported in the main body and having a sensordirected at the protection window, wherein the protection window isconfigured as a cylindrical lens or a toric lens with an optical power,and wherein, when the supplemental device is installed on the injectiondevice: a curved surface of the protection window that is furthest fromthe sensor arrangement at least partially wraps around the injectiondevice, and the curved surface of the protection window that is furthestfrom the sensor arrangement lies in close proximity with the dosagewindow of the injection device.
 2. A supplemental device as claimed inclaim 1, wherein the protection window is configured as a toric lens. 3.A supplemental device as claimed in claim 1, wherein the protectionwindow is configured as a cylindrical lens.
 4. A supplemental device asclaimed in claim 1, wherein a first portion of the protection window isconfigured as a cylindrical or toric lens and wherein a second portionof the protection window has a different optical power to the firstportion.
 5. A supplemental device as claimed in claim 1, comprising anillumination arrangement comprising one or more sources of light, eachof the one or more sources of light being directed at the protectionwindow.
 6. A supplemental device as claimed in claim 1, comprising anillumination arrangement comprising one or more sources of light, eachof the one or more sources of light being directed at the protectionwindow, wherein a first portion of the protection window is configuredas a cylindrical or toric lens, wherein a second portion of theprotection window has a different optical power to the first portion,wherein the first portion of the protection window is in an optical pathbetween the sensor arrangement and the dosage window of the injectiondevice when the injection device is in use, and wherein the secondportion of the protection window is not in the optical path between thesensor arrangement and the dosage window of the injection device whenthe injection device is in use but is in an optical path between theillumination arrangement and the dosage window of the injection devicewhen the injection device is in use.
 7. A supplemental device as claimedin claim 1, comprising an illumination arrangement comprising two ormore sources of light, each of the two or more sources of light beingdirected at the protection window, wherein the two or more sources oflight are located on opposite sides of the sensor arrangement, wherein acentral portion of the protection window is configured as a cylindricalor toric lens, wherein a periphery portion of the protection window hasa different optical power to the central portion, wherein the centralportion of the protection window is in an optical path between thesensor arrangement and the dosage window of the injection device whenthe injection device is in use, and wherein the periphery portion of theprotection window is not in the optical path between the sensorarrangement and the dosage window of the injection device when theinjection device is in use but is in an optical path between theillumination arrangement and the dosage window of the injection devicewhen the injection device is in use.
 8. A supplemental device as claimedin claim 1, wherein the protection window is formed of optical plastic.9. A supplemental device as claimed in claim 1, wherein the protectionwindow is provided with an anti-reflective coating on at least onesurface thereof.
 10. A supplemental device as claimed in claim 9,wherein the anti-reflective coating comprises plural dielectric layers.11. A supplemental device as claimed in claim 10, wherein theanti-reflective coating comprises between three and five dielectriclayers.
 12. A supplemental device as claimed in claim 1, wherein theprotection window is sealed to the main body so as to prevent ingress ofmaterial into the supplemental device around the protection window. 13.A system comprising the supplemental device and the injection device asclaimed in claim
 1. 14. A supplemental device for attachment to aninjection device including a dosage window covering a sleeve on whichdose values are marked, the supplemental device comprising: a main body;an arrangement for supporting the main body of the supplemental devicein a predetermined positional relationship with the injection device; atransparent protection window located at a surface of the main body thatis aligned with the dosage window of the injection device when in use;and a sensor arrangement supported in the main body and having a sensordirected at the protection window, wherein the protection window has anoptical power, and wherein, when the supplemental device is installed onthe injection device: a curved surface of the protection window that isfurthest from the sensor arrangement at least partially wraps around theinjection device, and the curved surface of the protection window thatis furthest from the sensor arrangement lies in close proximity with thedosage window of the injection device.
 15. A supplemental device asclaimed in claim 14, wherein the protection window is configured as atoric lens.
 16. A supplemental device as claimed in claim 14, whereinthe protection window is configured as a cylindrical lens.
 17. Asupplemental device as claimed in claim 14, wherein a first portion ofthe protection window has the optical power and wherein a second portionof the protection window has an optical power that is different than theoptical power of the first portion.
 18. A supplemental device as claimedin claim 14, comprising an illumination arrangement comprising one ormore sources of light, each of the one or more sources of light beingdirected at the protection window.
 19. A supplemental device as claimedin claim 14, comprising an illumination arrangement comprising one ormore sources of light, each of the one or more sources of light beingdirected at the protection window, wherein a first portion of theprotection window has the optical power, wherein a second portion of theprotection window has an optical power that is different than theoptical power of the first portion, wherein the first portion of theprotection window is in an optical path between the sensor arrangementand the dosage window of the injection device when the injection deviceis in use, and wherein the second portion of the protection window isnot in the optical path between the sensor arrangement and the dosagewindow of the injection device when the injection device is in use butis in an optical path between the illumination arrangement and thedosage window of the injection device when the injection device is inuse.
 20. A supplemental device as claimed in claim 14, comprising anillumination arrangement comprising two or more sources of light, eachof the two or more sources of light being directed at the protectionwindow, wherein the two or more sources of light are located on oppositesides of the sensor arrangement, wherein a central portion of theprotection window has the optical power, wherein a periphery portion ofthe protection window has an optical power that is different than theoptical power of the central portion, wherein the central portion of theprotection window is in an optical path between the sensor arrangementand the dosage window of the injection device when the injection deviceis in use, and wherein the periphery portion of the protection window isnot in the optical path between the sensor arrangement and the dosagewindow of the injection device when the injection device is in use butis in an optical path between the illumination arrangement and thedosage window of the injection device when the injection device is inuse.
 21. A supplemental device as claimed in claim 14, wherein theprotection window is formed of optical plastic.
 22. A supplementaldevice as claimed in claim 14, wherein the protection window is providedwith an anti-reflective coating on at least one surface thereof.
 23. Asupplemental device as claimed in claim 22, wherein the anti-reflectivecoating comprises plural dielectric layers.
 24. A supplemental device asclaimed in claim 23, wherein the anti-reflective coating comprisesbetween three and five dielectric layers.
 25. A supplemental device asclaimed in claim 14, wherein the protection window is sealed to the mainbody so as to prevent ingress of material into the supplemental devicearound the protection window.
 26. A system comprising the supplementaldevice and the injection device as claimed in claim 14.